Method of manufacture of high Young&#39;s modulus thermoelastic inkjet printer

ABSTRACT

A method of manufacturing a thermally actuated ink jet printhead includes the step of initially providing a wafer having a circuitry layer including the electrical circuitry necessary for the operation of a thermal actuator. A first sacrificial layer is deposited on the wafer and is etched. A Young&#39;s modulus layer is deposited to form a first layer of a thermal actuator and a portion of a nozzle chamber wall. A conductive heater material layer is provided and has a portion interconnected to the circuitry layer. A second sacrificial layer is deposited and etched in preparation for nozzle chamber walls. A nozzle wall material layer is deposited to form the walls of the nozzle chamber. The nozzle wall material layer is etched to define a nozzle port for the ejection of ink. The sacrificial layers are etched away to release the thermal actuator. The nozzle chamber walls are formed to define a fulcrum for the thermal actuator.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

CROSS-REFERENCED AUSTRALIAN U.S. PAT./PATENT APPLICATION PROVISIONALPATENT (CLAIMING RIGHT OF PRIORITY FROM APPLICATION NO. AUSTRALIANPROVISIONAL APPLICATION) DOCKET NO. PO7991 09/113,060 ART01 PO850509/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO801709/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO803209/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO803109/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO797909/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO798209/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO798009/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO801609/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO793909/112,785 ART29 PO8501 091112,797 ART30 PO8500 09/112,796 ART31 PO798709/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO802009/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO800009/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO799009/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO798109/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO802609/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO939409/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO939809/112,792 ART60 PO9399 6,106,147 ART61 PO9400 09/112,790 ART62 PO940109/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO940509/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP237009/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811,6,188,415 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP099309/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP259209/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP398709/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO793509/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO806109/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065 6,071,750 IJM06 PO805509/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO793309/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO806009/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126, 6,190,931IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074IJM27 PO8045 6,110,754 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832,6,180,427 IJM41 PP3990 09/112,831, 6,171,875 IJM42 PP3986 09/112,830IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775IR19 PP0880 6,152,619 IR20 PP0881 09/113,092 IR21 PO8006 6,087,638MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO80106,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947 6,067,797 MEMS07 PO794409/113,080 MEMS09 PO7946 6,044,646 MEMS10 PO9393 09/113,065 MEMS11PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

1. Field of the Invention

The present invention relates to the field of inkjet printing and, inparticular, discloses a method of manufacturing an ink jet printhead.

2. Background of the Invention

Many ink jet printing mechanisms are known. Unfortunately, in massproduction techniques, the production of ink jet printheads is quitedifficult. For example, often, the orifice or nozzle plate isconstructed separately from the ink supply and ink ejection mechanismand bonded to the mechanism at a later stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)). The separate material processing stepsrequired in handling such precision devices often adds a substantiallyexpense in manufacturing.

Additionally, side shooting ink jet technologies (U.S. Pat. No.4,899,181) are often used but again, this limit the amount of massproduction throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilised. Thesecan include electroforming of nickel stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laserablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

The utilisation of the above techniques is likely to add substantialexpense to the mass production of ink jet printheads and thereforesubstantially to their final cost.

It would therefore be desirable if an efficient system for the massproduction of ink jet printheads could be developed.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there isprovided a method of manufacture of a thermally actuated ink jet printercomprising a series of nozzle chambers which ejects ink via theutilization of a thermal actuator device, wherein said device has a highYoung's modulus comprising the steps of initially providing a siliconwafer having a circuitry wafer layer including the electrical circuitrynecessary for the operation of the thermal actuators on demand;depositing a first sacrificial layer on top of the silicon and circuitrywafer layer and etching said first sacrificial layer in an area defininga first portion of a nozzle chamber wall; depositing a first heatermaterial layer having a high young's modulus and forming a first layerof the thermal actuator and a portion of said nozzle chamber wall;depositing a second heater material layer being conductive and beingprovided for the heating of said first material layer and further havinga portion interconnected to said circuitry wafer layer for heating saidsecond heater material; depositing a second sacrificial layer andetching said second sacrificial layer for the construction of saidnozzle chamber walls; depositing a nozzle wall material layer to formthe walls of said nozzle chamber and etching said nozzle wall materiallayer to define a nozzle hole for the ejection of ink; etching away saidsacrificial layers to release said thermal actuator;

The method can further include etching an ink supply channel throughsaid wafer for the supply of ink to said nozzle chamber. The secondmaterial heater layer can comprise titanium diboride and said firstmaterial heater layer can comprise substantially glass. The sacrificialmaterial can comprise substantially aluminium and the nozzle chamberwalls can be constructed substantially from glass.

The nozzle chamber walls can include a thin membrane utilized by saidthermal actuator as a pivot point and the nozzle wall material layer caninclude a series of small etchant holes for assisting in the etching ofsaid sacrificial layers.

Preferably, an array of nozzles are formed on a single wafer layerutilizing planar monolithic deposition, lithographic and etchingprocesses. Standard vlsi/ulsi processing can be used. The silicon andcircuitry layer can comprise a CMOS process and the ink is ejected fromsaid substrate substantially normal to said substrate.

In accordance with a further aspect of the present invention, there isprovided a method of manufacturing a high young's modulus thermoelasticInkjet ink jet print head wherein an array of nozzles are formed on asubstrate utilising planar monolithic deposition, lithographic andetching processes.

Multiple ink jet printheads are preferably formed simultaneously on asingle planar substrate which can comprise a silicon wafer.

The printheads are preferably formed utilising standard vlsi/ulsiprocessing with the integrated drive electronics preferably formed onthe same substrate. The integrated drive electronics can comprise a CMOSprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 illustrates a single inkjet nozzle arrangement of the preferredembodiment;

FIG. 2 is an exploded perspective view of the arrangement of FIG. 1;

FIG. 3 shows a first stage in the operation of the ink jet nozzlearrangement of FIG. 1;

FIG. 4 shows an intermediate stage of operation of the ink jet nozzlearrangement of FIG. 1;

FIG. 5 shows a final stage, with an ink drop being ejected, in theoperation of the ink jet nozzle arrangement of FIG. 1.

FIG. 6 illustrates an array of nozzles formed in accordance with theinvention for utilisation in an inkjet printhead.

FIG. 7 provides a legend of the materials indicated in FIGS. 8 to 19;

FIG. 8 shows a wafer for use in a manufacturing process, in accordancewith the invention;

FIG. 9 shows the wafer of FIG. 8 etched to define a mask for an inkinlet channel;

FIG. 10 shows the wafer of FIG. 9 etched in preparation for a nozzlechamber wall and an actuator anchor point;

FIG. 11 shows the wafer of FIG. 10 with heater material depositedthereon;

FIG. 12 shows the wafer of FIG. 11 with the heater material etched todefine an actuator loop;

FIG. 13 shows the wafer of FIG. 12 with sacrificial material etched downto glass or heater material;

FIG. 14 shows the wafer of FIG. 13 with PECVD glass deposited thereon;

FIG. 15 shows the wafer of FIG. 14 etched to define a nozzle rim;

FIG. 16 shows the wafer of FIG. 15 etched to define a nozzle port andetch access holes;

FIG. 17 shows the wafer of FIG. 16 back etched to define an ink inletchannel;

FIG. 18 shows the wafer of FIG. 17 with sacrificial material etched tofree the actuators and separate the chips; and

FIG. 19 shows a completed printhead filled with ink for testing.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, the actuation of an actuator for theejection of ink is based around the utilisation of material having aHigh Young's modulus.

In the preferred embodiment, materials are utilised for the ejection ofink which have a high bend efficiency when thermally heated. The inkjetprint head is constructed utilising standard MEMS technology andtherefore should utilise materials that are common in the constructionof semi-conductor wafers. In the preferred embodiment, the materialshave been chosen through the utilisation of a bend efficiency foractuator devices which can be calculated in accordance with thefollowing formula.${{bend}\quad {efficiency}} = \frac{{Young}\text{'}s\quad {Modulus} \times \left( {{Coefficient}\quad {of}\quad {thermal}\quad {Expansion}} \right)}{{Density} \times {Specific}\quad {Heat}\quad {Capacity}}$

Of course, different equations could be utilised and, in particular, thefactors on the numerator and the denominator have been chosen for theirfollowing qualities.

Coefficient of thermal expansion: The greater the coefficient of thermalexpansion, the greater will be the degree of movement for any particularheating of a thermal actuator.

Young's Modulus: The Young's modulus provides a measure of the tensileor compressive stress of a material and is an indicator of the“strength” of the bending movement. Hence, a material having a highYoung's modulus or strength is desirable.

Heat capacity: In respect of the heat capacity, the higher the heatcapacity, the greater the ability of material to absorb heat withoutdeformation. This is an undesirable property in a thermal actuator.

Density: The denser the material the greater the heat energy required toheat the material and again, this is an undesirable property.

Example materials and their corresponding “Bend Efficiencies” are listedin the following table:

Young's Heat CTE modulus capacity Density “Bend MATERIAL *10⁻⁶/K GPaW/Kg/C Kg/M³ efficiency” Gold 14.2 80 129 19300 456 PTFE 770 1.3 1024  2130 459 Silicon Nitride 3.3 337 712  3200 488 Osmium 2.6 581 130 22570515 Tantalum- 6.48 186 140 16660 517 Tungsten alloy Silver 18.9 71 23510500 544 Platinum 8.8 177 133 21500 545 Copper 16.5 124 385  8960 593Molybdenum 4.8 323 251 10200 606 Alumimum 23.1 28.9 897  2700 657 Nickel13.4 206 444  8900 699 Tungsten 4.5 408 132 19300 721 Ruthenium 5.05 394247 12410 1067  Stainless Steel 20.2 215 500  7850 1106  Iridium 6.8 549130 22650 1268  High Silicon 31.5 130 376  8250 1320  Brass “Chromel D”25.2 212 448  7940 1502  alloy Titanium 8.2 575 636  4450 1666  DiBorideBoron Carbide 10.1 454 955  2520 1905 

From the above table, it can be seen that a suitable material istitanium diboride (TiB₂) which has a high bend efficiency and is alsoregularly used in semiconductor fabrication techniques. Although thismaterial has a High Young's modulus, the coefficient of thermalexpansion is somewhat lower than other possible materials. Hence, in thepreferred embodiment, a fulcrum arrangement is utilised to substantiallyincrease the travel of a material upon heating thereby more fullyutilizing the effect of the High Young's modulus material.

Turning initially to FIGS. 1 and 2, there is illustrated a single nozzle1 of an inkjet device constructed in accordance with the preferredembodiment. FIG. 1 illustrates a side perspective view of a singlenozzle and FIG. 2 is an exploded perspective of the arrangement of FIG.1. The single nozzle 1 can be constructed as part of an array of nozzlesformed on a silicon wafer 2 utilising standard MEM processingtechniques. On top of the silicon wafer 2 is formed a CMOS layer 3 whichcan include multiple metal layers formed within glass layers inaccordance with the normal CMOS methodologies.

The wafer 2 can contain a number of etched chambers eg. 33 (FIG. 2) thechambers being etched through the wafer utilising a deep trench siliconetcher.

A suitable plasma etching process can include a deep anisotropic trenchetching system such as that available from SDS Systems Limited (See“Advanced Silicon Etching Using High Density Plasmas” by J. K. Bhardwaj,H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in MicroMachining and Micro Fabrication Process Technology).

The preferred embodiment 1 includes two arms 4,5 which operate in airand are constructed from a thin 0.3 micrometer layer of titaniumdiboride 6 on top of a much thicker 5.8 micron layer of glass 7. The twoarms 4,5 are joined together and pivot around a point 9 which is a thinmembrane forming an enclosure which in turn forms part of the nozzlechamber 10.

The arms 4 and 5 are affixed by posts 11,12 to lower aluminiumconductive layers 14,15 which can form part of the CMOS layer 3. Theouter surfaces of the nozzle chamber 18 can be formed from glass ornitride and provide an enclosure to be filled with ink. The outerchamber 18 includes a number of etchant holes e.g. 19 which are providedfor the rapid sacrificial etching of internal cavities duringconstruction. A nozzle rim 20 is further provided around an ink ejectionport 21 for the ejection of ink.

The nozzle arrangement 1 includes a paddle 24 that is fabricated to beangled or bent away for the port 21. In use, a current is passed throughthe titanium boride layer 6 to cause heating of the layer 6 along arms 4and 5. The heating generally expands the T₁B₂ layer of arms 4 and 5which have a high Young's modulus. This expansion acts to bend the armsgenerally downwards, which are, as a result, pivoted about the membrane9. This pivoting results in a rapid upward movement of the paddle 24.The upward movement of the paddle 24 causes the ejection of ink from thenozzle port 21. The increase in pressure within the nozzle chamber 10 isinsufficient to overcome the surface tension characteristics of thesmaller etchant holes 19 that ink is ejected from the port 21.

As noted previously the thin titanium diboride layer 6 has asufficiently high young's modulus so as to cause the glass layer 7 to bebent upon heating of the titanium diboride layer 6. Hence, the operationof the inkjet device can be as illustrated in FIGS. 3-5. In itsquiescent state, the inkjet nozzle is as illustrated in FIG. 3, with thepaddle 24 generally in the bent down position an with an ink meniscus 30forming a slight bulge. The heating of the titanium diboride layer 6causes the layer 6 to expand. The glass layer 7 is subsequently bent tocause pivoting of the paddle 24 around the membrane wall 9 as indicatedin FIG. 4. This causes a rapid expansion of the meniscus 30 resulting inthe ejection of ink from the nozzle chamber 10. The current to thetitanium diboride layer is then discontinued and the paddle 24 returnsto its quiescent state resulting in a general drawing back of ink whichin turn results in the ejection of a drop 31 from the nozzle chamber 10.

Although many different alternatives are possible, the arrangement ofthe preferred embodiment can be constructed utilising the followingprocessing steps:

1. The starting wafer is a CMOS processed wafer with suitable electricalcircuitry for the operation of an array of printhead nozzles andincludes aluminium layer portions 14,15.

2. First, the CMOS wafer layer 3 can be etched down to the silicon waferlayer 2 in an area of the ink supply channel 34.

3. Next, a sacrificial layer can be constructed on top of the CMOS layerand planarised. A suitable sacrificial material can be aluminium. Thislayer is planarised, masked and etched to form cavities for the glasslayer 7. Subsequently, a glass layer is deposited on top of thesacrificial aluminium layer and etched so as to form the glass layer 7and lower layer 13.

4. A titanium diboride layer 6 is then deposited followed by thedeposition of a second sacrificial material layer, the material againcan be aluminium, the layer subsequently being planarised.

5. The sacrificial etchant layer is then etched to form cavities for thedeposition of the side walls eg. 9 of the top of the nozzle chamber 10.

6. A glass layer 52 is then deposited on top of the sacrificial layerand etched so as to form a roof of the chamber layer.

7. The rim 20, nozzle port 21 and etchant holes e.g. 19 can then beformed in the glass layer 52 utilising suitable etching processes.

8. The sacrificial aluminium layers are sacrificially etched away torelease the MEMS structure.

9. The ink supply channels can be formed by back etching the siliconwafer utilising a deep anisotropic trench etching system such as thatavailable from Silicon Technology Systems. The deep trench etchingsystems can also be utilised to separate printheads of a wafer which canthen be mounted on an ink supply system and tested for operationalcapabilities.

Turning finally to FIG. 6, there is illustrated a portion of a printhead40 showing a multi-coloured series of inkjet nozzles suitably arrangedto form a multi-coloured printhead. The portion is shown partially insection to illustrate the through wafer etching process.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed utilizing thefollowing steps:

1. Using a double sided polished wafer 2, complete drive transistors,data distribution, and timing circuits using a 0.5 micron, one poly, 2metal CMOS process 3. Relevant features of the wafer at this step areshown in FIG. 8. For clarity, these diagrams may not be to scale, andmay not represent a cross section though any single plane of the nozzle.FIG. 7 is a key to representations of various materials in thesemanufacturing diagrams, and those of other cross referenced ink jetconfigurations.

2. Etch oxide down to silicon or aluminum using Mask 1. This maskdefines the ink inlet, channel 34, a heater contact vias, and the edgesof the printhead chips. This step is shown in FIG. 9.

3. Deposit 1 micron of sacrificial material 50 (e.g. aluminum)

4. Etch the sacrificial layer using Mask 2, to define the nozzle chamberwall and the actuator anchor point. This step is shown in FIG. 10.

5. Deposit 3 microns of PECVD glass 13, and etch the glass 13 using Mask3. This mask defines the actuator, the nozzle walls, and the actuatoranchor points with the exception of the contact vias. The etch continuesthrough to aluminum.

6. Deposit 0.5 microns of heater material 6, for example titaniumnitride (TiN) or titanium diboride (TiB₂). This step is shown in FIG.11.

7. Etch the heater material using Mask 4, which defines an actuatorloop. This step is shown in FIG. 12.

8. Wafer probe. All electrical connections are complete at this point,bond pads are accessible, and the chips are not yet separated.

9. Deposit 8 microns of sacrificial material 51.

10. Etch the sacrificial material down to glass or heater material usingMask 5. This mask defines the nozzle chamber wall, the side walls e.g.9, and actuator anchor points. This step is shown in FIG. 13.

11. Deposit 3 microns of PECVD glass 52. This step is shown in FIG. 14.

12. Etch the glass 52 to a depth of 1 micron using Mask 6. This maskdefines the nozzle rim 20.

This step is shown in FIG. 15.

13. Etch down to the sacrificial layer using Mask 7. This mask definesthe nozzle port 21 and the sacrificial etch access holes 19. This stepis shown in FIG. 16.

14. Back-etch completely through the silicon wafer (with, for example,an ASE Advanced Silicon Etcher from Surface Technology Systems) usingMask 8. This mask defines the ink inlet channels 34 which are etchedthrough the wafer. The wafer is also diced by this etch. This step isshown in FIG. 17.

15. Etch the sacrificial material. The nozzle chambers 10 are cleared,the actuators freed, and the chips are separated by this etch. This stepis shown in FIG. 18.

16. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets at the back of the wafer.

17. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

18. Hydrophobize the front surface of the printheads.

19. Fill the completed printheads with ink 53 and test them. A fillednozzle is shown in FIG. 19.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing system including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters high speed pagewidth printers, notebook computers with in-builtpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic“minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the list under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is covered in U.S. patent application Ser. No.09/112,764, which is 0.35 mm wide, giving a chip area of 35 square mm.The printheads each contain 19,200 nozzles plus data and controlcircuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. Forty-five such inkjet typeswere filed simultaneously to the present application.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the forty-five examples can be made intoink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The simultaneously filed patent applications by the present applicantare listed by USSN numbers. In some cases, a print technology may belisted more than once in a table, where it shares characteristics withmore than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal ♦ Largeforce ♦ High power ♦ Canon Bubblejet bubble heater heats the ink togenerated ♦ Ink carrier 1979 Endo et al GB above boiling point, ♦ Simplelimited to water patent 2,007,162 transferring significant construction♦ Low efficiency ♦ Xerox heater-in- heat to the aqueous ♦ No movingparts ♦ High pit 1990 Hawkins et ink. A bubble ♦ Fast operationtemperatures al U.S. Pat. No. 4,899,181 nucleates and quickly ♦ Smallchip area required ♦ Hewlett-Packard forms, expelling the required foractuator ♦ High mechanical TIJ 1982 Vaught et ink. stress al U.S. Pat.No. 4,490,728 The efficiency of the ♦ Unusual process is low, withmaterials required typically less than ♦ Large drive 0.05% of theelectrical transistors energy being ♦ Cavitation causes transformed intoactuator failure kinetic energy of the ♦ Kogation reduces drop. bubbleformation ♦ Large print heads are difficult to fabricate Piezo- Apiezoelectric crystal ♦ Low power ♦ Very large area ♦ Kyser et al U.S.Pat. No. electric such as lead consumption required for actuator3,946,398 lanthanum zirconate ♦ Many ink types ♦ Difficult to ♦ ZoltanU.S. Pat. No. (PZT) is electrically can be used integrate with 3,683,212activated, and either ♦ Fast operation electronics ♦ 1973 Stemmeexpands, shears, or ♦ High efficiency ♦ High voltage U.S. Pat. No.3,747,120 bends to apply drive transistors ♦ Epson Stylus pressure tothe ink, required ♦ Tektronix ejecting drops. ♦ Full pagewidth ♦ IJ04print heads impractical due to actuator size ♦ Requires electricalpoling in high field strengths during manufacture Electro- An electricfield is ♦ Low power ♦ Low maximum ♦ Seiko Epson, strictive used toactivate consumption strain (approx. Usui et all JP electrostriction in♦ Many ink types 0.01%) 253401/96 relaxor materials such can be used ♦Large area ♦ IJ04 as lead lanthanum ♦ Low thermal required for actuatorzirconate titanate expansion due to low strain (PLZT) or lead ♦ Electricfield ♦ Response speed magnesium niobate strength required is marginal(˜10 (PMN). (approx. 3.5 V/μm) μs) can be generated ♦ High voltagewithout difficulty drive transistors ♦ Does not require requiredelectrical poling ♦ Full pagewidth print heads impractical due toactuator size Ferro- An electric field is ♦ Low power ♦ Difficult to ♦IJ04 electric used to induce a phase consumption integrate withtransition between the ♦ Many ink types electronics antiferroelectric(AFE) can be used ♦ Unusual and ferroelectric (FE) ♦ Fast operationmaterials such as phase. Perovskite (<1 μs) PLZSnT are materials such astin ♦ Relatively high required modified lead longitudinal strain ♦Actuators require lanthanum zirconate ♦ High efficiency a large areatitanate (PLZSnT) ♦ Electric field exhibit large strains of strength ofaround 3 up to 1% associated V/μm can be readily with the AFE to FEprovided phase transition. Electro- Conductive plates are ♦ Low power ♦Difficult to ♦ IJ02, IJ04 static plates separated by a consumptionoperate electrostatic compressible or fluid ♦ Many ink types devices inan dielectric (usually air). can be used aqueous Upon application of a ♦Fast operation environment voltage, the plates ♦ The electrostaticattract each other and actuator will displace ink, causing normally needto be drop ejection. The separated from the conductive plates may ink bein a comb or ♦ Very large area honeycomb structure, required to achieveor stacked to increase high forces the surface area and ♦ High voltagetherefore the force. drive transistors may be required ♦ Full pagewidthprint heads are not competitive due to actuator size Electro- A strongelectric field ♦ Low current ♦ High voltage ♦ 1989 Saito et al, staticpull is applied to the ink, consumption required U.S. Pat. No. 4,799,068on ink whereupon ♦ Low temperature ♦ May be damaged ♦ 1989 Miura et al,electrostatic attraction by sparks due to air U.S. Pat. No. 4,810,954accelerates the ink breakdown ♦ Tone-jet towards the print ♦ Requiredfield medium. strength increases as the drop size decreases ♦ Highvoltage drive transistors required ♦ Electrostatic field attracts dustPermanent An electromagnet ♦ Low power ♦ Complex ♦ IJ07, IJ10 magnetdirectly attracts a consumption fabrication electro- permanent magnet, ♦Many ink types ♦ Permanent magnetic displacing ink and can be usedmagnetic material causing drop ejection. ♦ Fast operation such asNeodymium Rare earth magnets ♦ High efficiency Iron Boron (NdFeB) with afield strength ♦ Easy extension required. around 1 Tesla can be fromsingle nozzles ♦ High local used. Examples are: to pagewidth printcurrents required Samarium Cobalt heads ♦ Copper (SaCo) and magneticmetalization should materials in the be used for long neodymium ironboron electromigration family (NdFeB, lifetime and low NdDyFeBNb,resistivity NdDyFeB, etc) ♦ Pigmented inks are usually infeasible ♦Operating temperature limited to the Curie temperature (around 540K)Soft A solenoid induced a ♦ Low power ♦ Complex ♦ IJ01, IJ05, IJ08,magnetic magnetic field in a soft consumption fabrication IJ10, IJ12,IJ14, core electro- magnetic core or yoke ♦ Many ink types ♦ Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such ♦ Fast operation CMOS fab such as aselectroplated iron ♦ High efficiency NiFe, CoNiFe, or alloys such asCoNiFe ♦ Easy extension CoFe are required [1], CoFe, or NiFe from singlenozzles ♦ High local alloys. Typically, the to pagewidth print currentsrequired soft magnetic material heads ♦ Copper is in two parts, whichmetalization should are normally held be used for long apart by aspring. electromigration When the solenoid is lifetime and low actuated,the two parts resistivity attract, displacing the ♦ Electroplating isink. required ♦ High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force ♦ Low power ♦ Forceacts as a ♦ IJ06, IJ11, IJ13, force acting on a current consumption ♦twisting motion IJ16 carrying wire in a ♦ Many ink types ♦ Typically,only a magnetic field is can be used quarter of the utilized. ♦ Fastoperation solenoid length This allows the ♦ High efficiency providesforce in a magnetic field to be ♦ Easy extension useful directionsupplied externally to from single nozzles ♦ High local the print head,for to pagewidth print currents required example with rare heads ♦Copper earth permanent metalization should magnets. be used for longOnly the current electromigration carrying wire need be lifetime and lowfabricated on the print- resistivity head, simplifying ♦ Pigmented inksmaterials are usually requirements. infeasible Magneto- The actuatoruses the ♦ Many ink types ♦ Force acts as a ♦ Fischenbeck, strictiongiant magnetostrictive can be used twisting motion U.S. Pat. No.4,032,929 effect of materials ♦ Fast operation ♦ Unusual ♦ IJ25 such asTerfenol-D (an ♦ Easy extension materials such as alloy of terbium, fromsingle nozzles Terfenol-D are dysprosium and iron to pagewidth printrequired developed at the Naval heads ♦ High local Ordnance Laboratory,♦ High force is currents required hence Ter-Fe-NOL). available ♦ CopperFor best efficiency, the metalization should actuator should be pre- beused for long stressed to approx. 8 electromigration MPa. lifetime andlow resistivity ♦ Pre-stressing may be required Surface Ink underpositive ♦ Low power ♦ Requires ♦ Silverbrook, EP tension pressure isheld in a consumption supplementary force 0771 658 A2 and reductionnozzle by surface ♦ Simple to effect drop related patent tension. Thesurface construction separation applications tension of the ink is ♦ Nounusual ♦ Requires special reduced below the materials required in inksurfactants bubble threshold, fabrication ♦ Speed may be causing the inkto ♦ High efficiency limited by surfactant egress from the ♦ Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is ♦ Simple ♦ Requires ♦ Silverbrook,EP reduction locally reduced to construction supplementary force 0771658 A2 and select which drops are ♦ No unusual to effect drop relatedpatent to be ejected. A materials required in separation applicationsviscosity reduction can fabrication ♦ Requires special be achieved ♦Easy extension ink viscosity electrothermally with from single nozzlesproperties most inks, but special to pagewidth print ♦ High speed isinks can be engineered heads difficult to achieve for a 100:1 viscosity♦ Requires reduction. oscillating ink pressure ♦ A high temperaturedifference (typically 80 degrees) is required Acoustic An acoustic waveis ♦ Can operate ♦ Complex drive ♦ 1993 Hadimioglu generated and withouta nozzle circuitry et al, EUP 550,192 focussed upon the plate ♦ Complex♦ 1993 Elrod et al, drop ejection region. fabrication EUP 572,220 ♦ Lowefficiency ♦ Poor control of drop position ♦ Poor control of drop volumeThermo- An actuator which ♦ Low power ♦ Efficient aqueous ♦ IJ03, IJ09,IJ17, elastic bend relies upon differential consumption operationrequires a IJ18, IJ19, IJ20, actuator thermal expansion ♦ Many ink typesthermal insulator on IJ21, IJ22, IJ23, upon Joule heating is can be usedthe hot side IJ24, IJ27, IJ28, used. ♦ Simple planar ♦ Corrosion IJ29,IJ30, IJ31, fabrication prevention can be IJ32, IJ33, IJ34, ♦ Small chiparea difficult IJ35, IJ36, IJ37, required for each ♦ Pigmented inks IJ38,IJ39, IJ40, actuator may be infeasible, IJ41 ♦ Fast operation aspigment particles ♦ High efficiency may jam the bend ♦ CMOS actuatorcompatible voltages and currents ♦ Standard MEMS processes can be used ♦Easy extension from single nozzles to pagewidth print heads High CTE Amaterial with a very ♦ High force can ♦ Requires special ♦ IJ09, IJ17,IJ18, thermo- high coefficient of be generated material (e.g. PTFE)IJ20, IJ21, IJ22, elastic thermal expansion ♦ Three methods of ♦Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as PTFE depositionare deposition process, IJ28, IJ29, IJ30, polytetrafluoroethylene underdevelopment: which is not yet IJ31, IJ42, IJ43, (PTFE) is used. Aschemical vapor standard in ULSI IJ44 high CTE materials deposition(CVD), fabs are usually non- spin coating, and ♦ PTFE depositionconductive, a heater evaporation cannot be followed fabricated from a ♦PTFE is a with high conductive material is, candidate for lowtemperature (above incorporated. A 50 μm dielectric constant 350° C.)processing long PTFE bend insulation in ULSI ♦ Pigmented inks actuatorwith ♦ Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input ♦ Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μm ♦Simple planar deflection. Actuator fabrication motions include: ♦ Smallchip area Bend required for each Push actuator Buckle ♦ Fast operationRotate ♦ High efficiency ♦ CMOS compatible voltages and currents ♦ Easyextension from single nozzles to pagewidth print heads Conduct-ive Apolymer with a high ♦ High force can ♦ Requires special ♦ IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such as♦ Very low power development (High elastic PTFE) is doped withconsumption CTE conductive actuator conducting substances ♦ Many inktypes polymer) to increase its can be used ♦ Requires a PTFEconductivity to about 3 ♦ Simple planar deposition process, orders ofmagnitude fabrication which is not yet below that of copper. ♦ Smallchip area standard in ULSI The conducting required for each fabs polymerexpands actuator ♦ PTFE deposition when resistively ♦ Fast operationcannot be followed heated. ♦ High efficiency with high Examples of ♦CMOS temperature (above conducting dopants compatible voltages 350° C.)processing include: and currents ♦ Evaporation and Carbon nanotubes ♦Easy extension CVD deposition Metal fibers from single nozzlestechniques cannot Conductive polymers to pagewidth print be used such asdoped heads ♦ Pigmented inks polythiophene may be infeasible, Carbongranules as pigment particles may jam the bend actuator Shape A shapememory alloy ♦ High force is ♦ Fatigue limits ♦ IJ26 memory such as TiNi(also available (stresses maximum number alloy known as Nitinol - ofhundreds of MPa) of cycles Nickel Titanium alloy ♦ Large strain is ♦ Lowstrain (1%) developed at the Naval available (more than is required toextend Ordnance Laboratory) 3%) fatigue resistance is thermally switched♦ High corrosion ♦ Cycle rate between its weak resistance limited byheat martensitic state and ♦ Simple removal its high stiffnessconstruction ♦ Requires unusual austenic state. The ♦ Easy extensionmaterials (TiNi) shape of the actuator from single nozzles ♦ The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape. ♦ Lowvoltage ♦ High current The shape change operation operation causesejection of a ♦ Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic ♦ Linear Magnetic ♦ Requires unusual ♦ IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using ♦ Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance ♦ Longactuator boron (NdFeB) Actuator (LSRA), and travel is available ♦Requires the Linear Stepper ♦ Medium force is complex multi- Actuator(LSA). available phase drive circuitry ♦ Low voltage ♦ High currentoperation operation BASIC OPERATION MODE Actuator This is the simplest ♦Simple operation ♦ Drop repetition ♦ Thermal inkjet directly mode ofoperation: the ♦ No external rate is usually ♦ Piezoelectric ink pushesink actuator directly fields required limited to around 10 jet suppliessufficient Satellite drops kHz. However, this ♦ IJ01, IJ02, IJ03,kinetic energy to expel can be avoided if is not fundamental IJ04, IJ05,IJ06, the drop. The drop drop velocity is less to the method, but isIJ07, IJ09, IJ11, must have a sufficient than 4 m/s related to therefill IJ12, IJ14, IJ16, velocity to overcome ♦ Can be efficient, methodnormally IJ20, IJ22, IJ23, the surface tension. depending upon the usedIJ24, IJ25, IJ26, actuator used ♦ All of the drop IJ27, IJ28, IJ29,kinetic energy must IJ30, IJ31, IJ32, be provided by the IJ33, IJ34,IJ35, actuator IJ36, IJ37, IJ38, ♦ Satellite drops IJ39, IJ40, IJ41,usually form if drop IJ42, IJ43, IJ44 velocity is greater than 4.5 m/sProximity The drops to be ♦ Very simple print ♦ Requires close ♦Silverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced ♦ The drop the print media orapplications. surface tension selection means transfer roller reductionof does not need to ♦ May require two pressurized ink). provide theenergy print heads printing Selected drops are required to separatealternate rows of the separated from the ink the drop from the image inthe nozzle by nozzle ♦ Monolithic color contact with the print printheads are medium or a transfer difficult roller. Electro- The drops tobe ♦ Very simple print ♦ Requires very ♦ Silverbrook, EP static pullprinted are selected by head fabrication can high electrostatic 0771 658A2 and on ink some manner (e.g. be used field related patent thermallyinduced ♦ The drop ♦ Electrostatic field applications surface tensionselection means for small nozzle ♦ Tone Jet reduction of does not needto sizes is above air pressurized ink). provide the energy breakdownSelected drops are required to separate ♦ Electrostatic field separatedfrom the ink the drop from the may attract dust in the nozzle by anozzle strong electric field. Magnetic The drops to be ♦ Very simpleprint ♦ Requires ♦ Silverbrook, EP pull on ink printed are selected byhead fabrication can magnetic ink 0771 658 A2 and some manner (e.g. beused ♦ Ink colors other related patent thermally induced ♦ The drop thanblack are applications surface tension selection means difficultreduction of does not need to ♦ Requires very pressurized ink). providethe energy high magnetic fields Selected drops are required to separateseparated from the ink the drop from the in the nozzle by a nozzlestrong magnetic field acting on the magnetic ink. Shutter The actuatormoves a ♦ High speed (>50 ♦ Moving parts are ♦ IJ13, IJ17, IJ21 shutterto block ink kHz) operation can required flow to the nozzle. The beachieved due to ♦ Requires ink ink pressure is pulsed reduced refilltime pressure modulator at a multiple of the ♦ Drop timing can ♦Friction and wear drop ejection be very accurate must be consideredfrequency. ♦ The actuator ♦ Stiction is energy can be very possible lowShuttered The actuator moves a ♦ Actuators with ♦ Moving parts are ♦IJ08, IJ15, IJ18, grill shutter to block ink small travel can berequired IJ19 flow through a grill to used ♦ Requires ink the nozzle.The shutter ♦ Actuators with pressure modulator movement need only smallforce can be ♦ Friction and wear be equal to the width used must beconsidered of the grill holes. ♦ High speed (>50 ♦ Stiction is kHz)operation can possible be achieved Pulsed A pulsed magnetic ♦ Extremelylow ♦ Requires an ♦ IJ10 magnetic field attracts an ‘ink energyoperation is external pulsed pull on ink pusher’ at the drop possiblemagnetic field pusher ejection frequency. An ♦ No heat ♦ Requiresspecial actuator controls a dissipation materials for both catch, whichprevents problems the actuator and the the ink pusher from ink pushermoving when a drop is ♦ Complex not to be ejected. constructionAUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) None The actuator directly♦ Simplicity of ♦ Drop ejection ♦ Most ink jets, fires the ink drop, andconstruction energy must be including there is no external ♦ Simplicityof supplied by piezoelectric and field or other operation individualnozzle thermal bubble. mechanism required. ♦ Small physical actuator ♦IJ01, IJ02, IJ03, size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20,IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33,IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44Oscillating The ink pressure ♦ Oscillating ink ♦ Requires external ♦Silverbrook, EP ink pressure oscillates, providing pressure can provideink pressure 0771 658 A2 and (including much of the drop a refill pulse,oscillator related patent acoustic ejection energy. The allowing higher♦ Ink pressure applications stimul- actuator selects which operatingspeed phase and amplitude ♦ IJ08, IJ13, IJ15, ation) drops are to befired ♦ The actuators must be carefully IJ17, IJ18, IJ19, by selectivelymay operate with controlled IJ21 blocking or enabling much lower energy♦ Acoustic nozzles. The ink ♦ Acoustic lenses reflections in the inkpressure oscillation can be used to focus chamber must be may beachieved by the sound on the designed for vibrating the print nozzleshead, or preferably by an actuator in the ink supply. Media The printhead is ♦ Low power ♦ Precision ♦ Silverbrook, EP proximity placed inclose ♦ High accuracy assembly required 0771 658 A2 and proximity to theprint ♦ Simple print head ♦ Paper fibers may related patent medium.Selected construction cause problems applications drops protrude from ♦Cannot print on the print head further rough substrates than unselecteddrops, and contact the print medium. The drop soaks into the medium fastenough to cause drop separation. Transfer Drops are printed to a ♦ Highaccuracy ♦ Bulky ♦ Silverbrook, EP roller transfer roller instead ♦ Widerange of ♦ Expensive 0771 658 A2 and of straight to the print printsubstrates can ♦ Complex related patent medium. A transfer be usedconstruction applications roller can also be used ♦ Ink can be dried ♦Tektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. inkjet ♦ Any of the IJ series Electro- Anelectric field is ♦ Low power ♦ Field strength ♦ Silverbrook, EP staticused to accelerate ♦ Simple print head required for 0771 658 A2 andselected drops towards construction separation of small related patentthe print medium. drops is near or applications above air ♦ Tone-Jetbreakdown Direct A magnetic field is ♦ Low power ♦ Requires ♦Silverbrook, EP magnetic used to accelerate ♦ Simple print head magneticink 0771 658 A2 and field selected drops of construction ♦ Requiresstrong related patent magnetic ink towards magnetic field applicationsthe print medium. Cross The print head is ♦ Does not require ♦ Requiresexternal ♦ IJ06, IJ16 magnetic placed in a constant magnetic materialsmagnet field magnetic field. The to be integrated in ♦ Current densitiesLorenz force in a the print head may be high, current carrying wiremanufacturing resulting in is used to move the process electromigrationactuator. problems Pulsed A pulsed magnetic ♦ Very low power ♦ Complexprint ♦ IJ10 magnetic field is used to operation is possible headconstruction field cyclically attract a ♦ Small print head ♦ Magneticpaddle, which pushes size materials required in on the ink. A smallprint head actuator moves a catch, which selectively prevents the paddlefrom moving. ACTUATOR AMPLIFICATION OR MODIFICATION METHOD None Noactuator ♦ Operational ♦ Many actuator ♦ Thermal Bubble mechanicalsimplicity mechanisms have Ink jet amplification is used. insufficienttravel, ♦ IJ01, IJ02, IJ06, The actuator directly or insufficient force,IJ07, IJ16, IJ25, drives the drop to efficiently drive IJ26 ejectionprocess. the drop ejection process Differential An actuator material ♦Provides greater ♦ High stresses are ♦ Piezoelectric expansion expandsmore on one travel in a reduced involved ♦ IJ03, IJ09, IJ17, bend sidethan on the other. print head area ♦ Care must be IJ18, IJ19, IJ20,actuator The expansion may be taken that the IJ21, IJ22, IJ23, thermal,piezoelectric, materials do not IJ24, IJ27, IJ29, magnetostrictive, ordelaminate IJ30, IJ31, IJ32, other mechanism. The Residual bend IJ33,IJ34, IJ35, bend actuator converts resulting from high IJ36, IJ37, IJ38,a high force low travel temperature or high IJ39, IJ42, IJ43, actuatormechanism to stress during IJ44 high travel, lower formation forcemechanism. Transient A trilayer bend ♦ Very good High stresses are ♦IJ40, IJ41 bend actuator where the two temperature stability involvedactuator outside layers are ♦ High speed, as a ♦ Care must be identical.This cancels new drop can be taken that the bend due to ambient firedbefore heat materials do not temperature and dissipates delaminateresidual stress. The ♦ Cancels residual actuator only responds stress offormation to transient heating of one side or the other. Reverse Theactuator loads a ♦ Better coupling ♦ Fabrication ♦ IJ05, IJ11 springspring. When the to the ink complexity actuator is turned off, ♦ Highstress in the the spring releases. spring This can reverse theforce/distance curve of the actuator to make it compatible with theforce/time requirements of the drop ejection. Actuator A series of thin♦ Increased travel ♦ Increased ♦ Some stack actuators are stacked. ♦Reduced drive fabrication piezoelectric inkjets This can be voltagecomplexity ♦ IJ04 appropriate where ♦ Increased actuators require highpossibility of short electric field strength, circuits due to such aselectrostatic pinholes and piezoelectric actuators. Multiple Multiplesmaller ♦ Increases the ♦ Actuator forces ♦ IJ12, IJ13, IJ18, actuatorsactuators are used force available from may not add IJ20, IJ22, IJ28,simultaneously to an actuator linearly, reducing IJ42, IJ43 move theink. Each ♦ Multiple efficiency actuator need provide actuators can beonly a portion of the positioned to control force required. ink flowaccurately Linear A linear spring is used ♦ Matches low ♦ Requires print♦ IJ15 Spring to transform a motion travel actuator with head area forthe with small travel and higher travel spring high force into arequirements longer travel, lower ♦ Non-contact force motion. method ofmotion transformation Coiled A bend actuator is ♦ Increases travel ♦Generally ♦ IJ17, IJ21, IJ34, actuator coiled to provide ♦ Reduces chiprestricted to planar IJ35 greater travel in a area implementationsreduced chip area. ♦ Planar due to extreme implementations arefabrication difficulty relatively easy to in other orientations.fabricated Flexure A bend actuator has a ♦ Simple means of ♦ Care mustbe ♦ IJ10, IJ19, IJ33 bend small region near the increasing travel oftaken not to exceed actuator fixture point, which a bend actuator theelastic limit in flexes much more the flexure area readily than the ♦Stress remainder of the distribution is very actuator. The actuatoruneven flexing is effectively ♦ Difficult to converted from anaccurately model even coiling to an with finite element angular bend,resulting analysis in greater travel of the actuator tip. Catch Theactuator controls a ♦ Very low ♦ Complex ♦ IJ10 small catch. The catchactuator energy construction either enables or ♦ Very small ♦ Requiresexternal disables movement of actuator size force an ink pusher that is♦ Unsuitable for controlled in a bulk pigmented inks manner. Gears Gearscan be used to ♦ Low force, low ♦ Moving parts are ♦ IJ10 increasetravel at the travel actuators can required expense of duration. be used♦ Several actuator Circular gears, rack ♦ Can be fabricated cycles arerequired and pinion, ratchets, using standard ♦ More complex and othergearing surface MEMS drive electronics methods can be used. processes ♦Complex construction ♦ Friction, friction, and wear are possibleleBuckle plate A buckle plate can be ♦ Very fast ♦ Must stay within ♦ S.Hirata et al, used to change a slow movement elastic limits of the “AnInk-jet Head actuator into a fast achievable materials for long UsingDiaphragm motion. It can also device life Microactuator”, convert a highforce, ♦ High stresses Proc. IEEE MEMS, low travel actuator involvedFeb. 1996, pp 418- into a high travel, ♦ Generally high 423. mediumforce motion. power requirement ♦ IJ18, IJ27 Tapered A tapered magnetic♦ Linearizes the ♦ Complex ♦ IJ14 magnetic pole can increase magneticconstruction pole travel at the expense forced/distance curve of force.Lever A lever and fulcrum is ♦ Matches low ♦ High stress ♦ IJ12, IJ36,IJ37 used to transform a travel actuator with around the fulcrum motionwith small higher travel travel and high force requirements into amotion with ♦ Fulcrum area has longer travel and no linear movement,lower force. The lever and can be used for can also reverse the a fluidseal direction of travel. Rotary The actuator is ♦ High mechanical ♦Complex ♦ IJ28 impeller connected to a rotary advantage constructionimpeller. A small ♦ The ratio of force ♦ Unsuitable for angulardeflection of to travel of the pigmented inks the actuator results inactuator can be a rotation of the matched to the impeller vanes, whichnozzle requirements push the ink against by varying the stationary vanesand number of impeller out of the nozzle. vanes Acoustic A refractive or♦ No moving parts ♦ Large area ♦ 1993 Hadimioglu lens diffractive (e.g.zone required et al, EUP 550,192 plate) acoustic lens is ♦ Only relevantfor ♦ 1993 Elrod et al, used to concentrate acoustic ink jets EUP572,220 sound waves. Sharp A sharp point is used ♦ Simple ♦ Difficult to♦ Tone-jet conductive to concentrate an construction fabricate usingpoint electrostatic field. standard VLSI processes for a surfaceejecting ink- jet ♦ Only relevant for electrostatic ink jets ACTUATORMOTION Volume The volume of the ♦ Simple ♦ High energy is ♦Hewlett-Packard expansion actuator changes, construction in thetypically required to Thermal Ink jet pushing the ink in all case ofthermal ink achieve volume ♦ Canon Bubblejet directions. jet expansion.This leads to thermal stress, cavitation, and kogation in thermal inkjet implementations Linear, The actuator moves in ♦ Efficient ♦ Highfabrication ♦ IJ01, IJ02, IJ04, normal to a direction normal to couplingto ink complexity may be IJ07, IJ11, IJ14 chip surface the print headsurface. drops ejected required to achieve The nozzle is typicallynormal to the perpendicular in the line of surface motion movement.Parallel to The actuator moves ♦ Suitable for ♦ Fabrication ♦ IJ12,IJ11, IJ15, chip surface parallel to the print planar fabricationcomplexity IJ33, IJ34, IJ35, head surface. Drop ♦ Friction IJ36 ejectionmay still be ♦ Stiction normal to the surface. Membrane An actuator witha ♦ The effective ♦ Fabrication ♦ 1982 Hawkins push high force but smallarea of the actuator complexity U.S. Pat. No. 4,459,601 area is used topush a becomes the ♦ Actuator size stiff membrane that is membrane area♦ Difficulty of in contact with the ink. integration in a VLSI processRotary The actuator causes ♦ Rotary levers ♦ Device ♦ IJ05, IJ08, IJ11,the rotation of some may be used to complexity IJ28 element, such agrill or increase travel ♦ May have impeller ♦ Small chip area frictionat a pivot requirements point Bend The actuator bends ♦ A very small ♦Requires the ♦ 1970 Kyser et al when energized. This change in actuatorto be made U.S. Pat. No. 3,946,398 may be due to dimensions can be fromat least two 1973 Stemme differential thermal converted to a largedistinct layers, or to U.S. Pat. No. 3,747,120 expansion, motion. have athermal ♦ IJ03, IJ09, IJ10, piezoelectric difference across the IJ19,IJ23, IJ24, expansion, actuator IJ25, IJ29, IJ30, Magnetostriction, orIJ31, IJ33, IJ34, other form of relative IJ35 dimensional change. SwivelThe actuator swivels ♦ Allows operation ♦ Inefficient ♦ IJ06 around acentral pivot. where the net linear coupling to the ink This motion issuitable force on the paddle motion where there are is zero oppositeforces ♦ Small chip area applied to opposite requirements sides of thepaddle, e.g. Lorenz force. Straighten The actuator is ♦ Can be used with♦ Requires careful ♦ IJ26, IJ32 normally bent, and shape memory balanceof stresses straightens when alloys where the to ensure that theenergized. austenic phase is quiescent bend is planar accurate DoubleThe actuator bends in ♦ One actuator can ♦ Difficult to make ♦ IJ36,IJ37, 1IJ8 bend one direction when be used to power the drops ejected byone element is two nozzles. both bend directions energized, and bends ♦Reduced chip identical. the other way when size. ♦ A small anotherelement is ♦ Not sensitive to efficiency loss energized. ambienttemperature compared to equivalent single bend actuators. ShearEnergizing the ♦ Can increase the ♦ Not readily ♦ 1985 Fishbeck actuatorcauses a shear effective travel of applicable to other U.S. Pat. No.4,584,590 motion in the actuator piezoelectric actuator material.actuators mechanisms Radial con- The actuator squeezes ♦ Relatively easy♦ High force ♦ 1970 Zoltan U.S. Pat. No. striction an ink reservoir, tofabricate single required 3,683,212 forcing ink from a nozzles fromglass ♦ Inefficient constricted nozzle. tubing as ♦ Difficult tomacroscopic integrate with VLSI structures processes Coil/uncoil Acoiled actuator ♦ Easy to fabricate ♦ Difficult to ♦ IJ17, IJ21, 1IJ4,uncoils or coils more as a planar VLSI fabricate for non- IJ35 tightly.The motion of process planar devices the free end of the ♦ Small area ♦Poor out-of-plane actuator ejects the ink. required, therefore stiffnesslow cost Bow The actuator bows (or ♦ Can increase the ♦ Maximum travel ♦IJ16, IJ18, IJ27 buckles) in the middle speed of travel is constrainedwhen energized. ♦ Mechanically ♦ High force rigid required Push-Pull Twoactuators control ♦ The structure is ♦ Not readily ♦ IJ18 a shutter. Oneactuator pinned at both ends, suitable for ink jets pulls the shutter,and so has a high out-of- which directly push the other pushes it. planerigidity the ink Curl A set of actuators curl ♦ Good fluid flow ♦ Design♦ IJ20, IJ42 inwards inwards to reduce the to the region behindcomplexity volume of ink that the actuator they enclose. increasesefficiency Curl A set of actuators curl ♦ Relatively simple ♦ Relativelylarge ♦ IJ43 outwards outwards, pressurizing construction chip area inkin a chamber surrounding the actuators, and expelling ink from a nozzlein the chamber. Iris Multiple vanes enclose ♦ High efficiency ♦ Highfabrication ♦ IJ22 a volume of ink. These ♦ Small chip area complexitysimultaneously rotate, ♦ Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates ♦ The actuatorcan ♦ Large area ♦ 1993 Hadimioglu vibration at a high frequency. bephysically distant required for et al, EUP 550, 192 from the inkefficient operation ♦ 1993 Elrod et al, at useful frequencies EUP572,220 ♦ Acoustic coupling and crosstalk ♦ Complex drive circuitry ♦Poor control of drop volume and position None In various ink jet ♦ Nomoving parts ♦ Various other ♦ Silverbrook, EP designs the actuatortrade-offs are 0771 658 A2 and does not move. required to related patenteliminate moving applications parts ♦ Tone-jet NOZZLE REFILL METHODSurface This is the normal way ♦ Fabrication ♦ Low speed ♦ Thermal inkjet tension that inkjets are simplicity ♦ Surface tension ♦Piezoelectric ink refilled. After the ♦ Operational force relatively jetactuator is energized, simplicity small compared to ♦ IJ01-IJ07, IJ10-it typically returns actuator force IJ14, IJ16, IJ20, rapidly to itsnormal ♦ Long refill time IJ22-IJ45 position. This rapid usuallydominates return sucks in air the total repetition through the nozzlerate opening. The ink surface tension at the nozzle then exerts a smallforce restoring the meniscus to a minimum area. This force refills thenozzle. Shuttered Ink to the nozzle ♦ High speed ♦ Requires ♦ IJ08,IJ13, IJ15, oscillating chamber is provided at ♦ Low actuator common inkIJ17, IJ18, IJ19, ink pressure a pressure that energy, as the pressureoscillator IJ21 oscillates at twice the actuator need only ♦ May not bedrop ejection open or close the suitable for frequency. When a shutter,instead of pigmented inks drop is to be ejected, ejecting the ink dropthe shutter is opened for 3 half cycles: drop ejection, actuator return,and refill. The shutter is then closed to prevent the nozzle chamberemptying during the next negative pressure cycle. Refill After the main♦ High speed, as ♦ Requires two ♦ IJ09 actuator actuator has ejected athe nozzle is independent drop a second (refill) actively refilledactuators per nozzle actuator is energized. The refill actuator pushesink into the nozzle chamber. The refill actuator returns slowly, toprevent its return from emptying the chamber again. Positive ink The inkis held a slight ♦ High refill rate, ♦ Surface spill ♦ Silverbrook, EPpressure positive pressure. therefore a high must be prevented 0771 658A2 and After the ink drop is drop repetition rate ♦ Highly relatedpatent ejected, the nozzle is possible hydrophobic print applicationschamber fills quickly head surfaces are ♦ Alterative for:, as surfacetension and required IJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20,IJ22-IJ45 operate to refill the nozzle. METHOD OF RESTRICTING BACK-FLOWTHROUGH INLET Long inlet The ink inlet channel ♦ Design simplicity ♦Restricts refill ♦ Thermal inkjet channel to the nozzle chamber ♦Operational rate ♦ Piezoelectric ink is made long and simplicity ♦ Mayresult in a jet relatively narrow, ♦ Reduces relatively large chip ♦IJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet ♦ Onlypartially back-flow. effective Positive ink The ink is under a ♦ Dropselection ♦ Requires a ♦ Silverbrook, EP pressure positive pressure, soand separation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes ♦ Fast refill timehydrophobizing, or ♦ Possible from the nozzle. both) to preventoperation of the This reduces the flooding of the following: IJ01-pressure in the nozzle ejection surface of IJ07, IJ09-IJ12, chamberwhich is the print head. IJ14, IJ16, IJ20, required to eject a IJ22, ,IJ23-IJ34, certain volume of ink. IJ36-IJ41, IJ44 The reduction inchamber pressure results in a reduction in ink pushed out through theinlet. Baffle One or more baffles ♦ The refill rate is ♦ Design ♦ HPThermal Ink are placed in the inlet not as restricted as complexity Jetink flow. When the the long inlet ♦ May increase ♦ Tektronix actuator isenergized, method. fabrication piezoelectric inkjet the rapid ink ♦Reduces complexity (e.g. movement creates crosstalk Tektronix hot melteddies which restrict Piezoelectric print the flow through the heads).inlet. The slower refill process is unrestricted, and does not result ineddies. Flexible flap In this method recently ♦ Significantly ♦ Notapplicable to ♦ Canon restricts disclosed by Canon, reduces back-flowmost ink jet inlet the expanding actuator for edge-shooterconfigurations (bubble) pushes on a thermal ink jet ♦ Increased flexibleflap that devices fabrication restricts the inlet. complexity ♦Inelastic deformation of polymer flap results in creep over extended useInlet filter A filter is located ♦ Additional ♦ Restricts refill ♦ IJ04,IJ12, IJ24, between the ink inlet advantage of ink rate IJ27, IJ29, IJ30and the nozzle filtration ♦ May result in chamber. The filter ♦ Inkfilter may be complex has a multitude of fabricated with no constructionsmall holes or slots, additional process restricting ink flow. steps Thefilter also removes particles which may block the nozzle. Small inletThe ink inlet channel ♦ Design simplicity ♦ Restricts refill ♦ IJ02,IJ37, IJ44 compared to the nozzle chamber rate to nozzle has asubstantially ♦ May result in a smaller cross section relatively largechip than that of the nozzle area resulting in easier ink ♦ Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator ♦ Increases speed ♦ Requires separate♦ IJ09 controls the position of of the ink-jet print refill actuator anda shutter, closing off head operation drive circuit the ink inlet whenthe main actuator is energized. The inlet is The method avoids the ♦Back-flow ♦ Requires careful ♦ IJ01, IJ03, IJ05, located problem ofinlet back- problem is design to minimize IJ06, IJ07, IJ10, behind theflow by arranging the eliminated the negative IJ11, IJ14, IJ16,ink-pushing ink-pushing surface of pressure behind the IJ22, IJ23, 1125,surface the actuator between paddle IJ28, IJ31, IJ32, the inlet and theIJ33, IJ34, IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the Theactuator and a ♦ Significant ♦ Small increase in ♦ IJ07, IJ20, IJ26,actuator wall of the ink reductions in back- fabrication IJ38 moves tochamber are arranged flow can be complexity shut off the so that themotion of achieved inlet the actuator closes off ♦ Compact designs theinlet. possible Nozzle In some configurations ♦ Ink back-flow ♦ Nonerelated to ♦ Silverbrook, EP actuator of inkjet, there is no problem isink back-flow on 0771 658 A2 and does not expansion or eliminatedactuation related patent result in ink movement of an applicationsback-flow actuator which may ♦ Valve-jet cause ink back-flow ♦ Tone-jetthrough the inlet. NOZZLE CLEARING METHOD Normal All of the nozzles are♦ No added ♦ May not be ♦ Most inkjet nozzle firing fired periodically,complexity on the sufficient to systems before the ink has a print headdisplace dried ink ♦ IJ01, IJ02, IJ03, chance to dry. When IJ04, IJ05,IJ06, not in use the nozzles IJ07, IJ09, IJ10, are sealed (capped) IJ11,IJ12, IJ14, against air. IJ16, IJ20, IJ22, The nozzle firing is IJ23,IJ24, IJ25, usually performed IJ26, IJ27, IJ28, during a special IJ29,IJ30, IJ31, clearing cycle, after IJ32, IJ33, IJ34, first moving theprint IJ36, IJ37, IJ38, head to a cleaning IJ39, IJ40, IJ41, station.IJ42, IJ43, IJ44, IJ45 Extra In systems which heat ♦ Can be highly ♦Requires higher ♦ Silverbrook, EP power to the ink, but do not boileffective if the drive voltage for 0771 658 A2 and ink heater it undernormal heater is adjacent to clearing related patent situations, nozzlethe nozzle ♦ May require applications clearing can be larger driveachieved by over- transistors powering the heater and boiling ink at thenozzle. Rapid The actuator is fired in ♦ Does not require ♦Effectiveness ♦ May be used succession rapid succession. In extra drivecircuits depends with: IJ01, IJ02, of actuator some configurations, onthe print head substantially upon IJ03, IJ04, IJ05, pulses this maycause heat ♦ Can be readily the configuration of IJ06, IJ07, IJ09,build-up at the nozzle controlled and the inkjet nozzle IJ10, IJ11,IJ14, which boils the ink, initiated by digital IJ16, IJ20, IJ22,clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations, it mayIJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrations todislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is ♦ A simple ♦ Notsuitable ♦ May be used power to not normally driven to solution wherewhere there is a with: IJ03, IJ09, ink pushing the limit of its motion,applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing maybe actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30,IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41,IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is ♦ A high nozzle ♦High ♦ IJ08, IJ13, IJ15, resonance applied to the ink clearingcapability implementation cost IJ17, IJ18, IJ19, chamber. This wave iscan be achieved if system does not IJ21 of an appropriate ♦ May bealready include an amplitude and implemented at very acoustic actuatorfrequency to cause low cost in systems sufficient force at the whichalready nozzle to clear include acoustic blockages. This is actuatorseasiest to achieve if the ultrasonic wave is at a resonant frequency ofthe ink cavity. Nozzle A microfabricated ♦ Can clear ♦ Accurate ♦Silverbrook, EP clearing plate is pushed against severely cloggedmechanical 0771 658 A2 and plate the nozzles. The plate nozzlesalignment is related patent has a post for every required applicationsnozzle. A post moves ♦ Moving parts are through each nozzle, requireddisplacing dried ink. ♦ There is risk of damage to the nozzles ♦Accurate fabrication is required Ink The pressure, of the ink ♦ May beeffective ♦ Requires ♦ May be used pressure is temporarily where otherpressure pump or with all IJ series ink pulse increased so that inkmethods cannot be other pressure jets streams from all of the usedactuator nozzles. This may be ♦ Expensive used in conjunction ♦ Wastefulof ink with actuator energizing. Print head A flexible ‘blade’ is ♦Effective for ♦ Difficult to use if ♦ Many ink jet wiper wiped acrossthe print planar print head print head surface is systems head surface.The surfaces non-planar or very blade is usually ♦ Low cost fragilefabricated from a ♦ Requires flexible polymer, e.g. mechanical partsrubber or synthetic ♦ Blade can wear elastomer. out in high volume printsystems Separate A separate heater is ♦ Can be effective ♦ Fabrication ♦Can be used with ink boiling provided at the nozzle where other nozzlecomplexity many IJ series ink heater although the normal clearingmethods jets drop e-ection cannot be used mechanism does not ♦ Can berequire it. The heaters implemented at no do not require additional costin individual drive some ink jet circuits, as many configurationsnozzles can be cleared simultaneously, and no imaging is required.NOZZLE PLATE CONSTRUCTION Electro- A nozzle plate is ♦ Fabrication ♦High ♦ Hewlett Packard formed separately fabricated simplicitytemperatures and Thermal Ink jet nickel from electroformed pressures arenickel, and bonded to required to bond the print head chip. nozzle plate♦ Minimum thickness constraints ♦ Differential thermal expansion LaserIndividual nozzle ♦ No masks ♦ Each hole must ♦ Canon Bubblejet ablatedor holes are ablated by an required be individually ♦ 1988 Sercel etdrilled intense UV laser in a ♦ Can be quite fast formed al., SPIE, Vol.998 polymer nozzle plate, which is ♦ Some control ♦ Special Excimer Beamtypically a polymer over nozzle profile equipment required Applications,pp. such as polyimide or is possible ♦ Slow where there 76-83.polysulfone ♦ Equipment are many thousands ♦ 1993 Watanabe required isrelatively of nozzles per print et al., U.S. Pat. No. low cost head5,208,604 ♦ May produce thin burrs at exit holes Silicon A separatenozzle ♦ High accuracy is ♦ Two part ♦ K. Bean, IEEE micro- plate isattainable construction Transactions on machined micromachined from ♦High cost Electron Devices, single crystal silicon, ♦ Requires Vol.ED-25, No. 10, and bonded to the precision alignment 1978, pp 1185-1195print head wafer. ♦ Nozzles may be ♦ Xerox 1990 clogged by adhesiveHawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries ♦No expensive ♦ Very small ♦ 1970 Zoltan U.S. Pat. No. capillaries aredrawn from glass equipment required nozzle sizes are 3,683,212 tubing.This method ♦ Simple to make difficult to form has been used for singlenozzles ♦ Not suited for making individual mass production nozzles, butis difficult to use for bulk manufacturing of print heads with thousandsof nozzles. Monolithic, The nozzle plate is ♦ High accuracy ♦ Requires ♦Silverbrook, EP surface deposited as a layer (<1 μm) sacrificial layer0771 658 A2 and micro- using standard VLSI ♦ Monolithic under the nozzlerelated patent machined deposition techniques. ♦ Low cost plate to formthe applications using VLSI Nozzles are etched in ♦ Existing nozzlechamber ♦ IJ01, IJ02, IJ04, litho- the nozzle plate using processes canbe ♦ Surface may be IJ11, IJ12, IJ17, graphic VLSI lithography and usedfragile to the touch IJ18, IJ20, IJ22, processes etching. IJ24, IJ27,IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a ♦ High accuracy♦ Requires long ♦ IJ03, IJ05, IJ06, etched buried etch stop in the (<1μm) etch times IJ07, IJ08, IJ09, through wafer. Nozzle ♦ Monolithic ♦Requires a IJ10, IJ13, IJ14, substrate chambers are etched in ♦ Low costsupport wafer IJ15, IJ16, IJ19, the front of the wafer, ♦ Nodifferential IJ21, IJ23, IJ25, and the wafer is expansion IJ26 thinnedfrom the back side. Nozzles are then etched in the etch stop layer. Nonozzle Various methods have ♦ No nozzles to ♦ Difficult to ♦ Ricoh 1995plate been tried to eliminate become clogged control drop Sekiya et alU.S. Pat. No. the nozzles entirely, to position accurately 5,412,4IJprevent nozzle Crosstalk ♦ 1993 Hadimioglu clogging. These problems etal EUP 550,192 include thermal bubble ♦ 1993 Elrod et al mechanisms andEUP 572,220 acoustic lens mechanisms Trough Each drop ejector has ♦Reduced ♦ Drop firing ♦ IJ35 a trough through manufacturing direction issensitive which a paddle moves. complexity to wicking. There is nonozzle ♦ Monolithic plate. Nozzle slit The elimination of ♦ No nozzlesto ♦ Difficult to ♦ 1989 Saito et al instead of nozzle holes and becomeclogged control drop U.S. Pat. No. 4,799,068 individual replacement by aslit position accurately nozzles encompassing many ♦ Crosstalk actuatorpositions problems reduces nozzle clogging, but increases crosstalk dueto ink surface waves DROP EJECTION DIRECTION Edge Ink flow is along the♦ Simple ♦ Nozzles limited ♦ Canon Bubblejet (‘edge surface of the chip,construction to edge 1979 Endo et al GB shooter’) and ink drops are ♦ Nosilicon ♦ High resolution patent 2,007,162 ejected from the chip etchingrequired is difficult ♦ Xerox heater-in- edge. ♦ Good heat ♦ Fast colorpit 1990 Hawkins et sinking via substrate printing requires al U.S. Pat.No. 4,899,181 ♦ Mechanically one print head per ♦ Tone-jet strong color♦ Ease of chip handing Surface Ink flow is along the ♦ No bulk silicon ♦Maximum ink ♦ Hewlett-Packard (‘roof surface of the chip, etchingrequired flow is severely TIJ 1982 Vaught et shooter') and ink drops are♦ Silicon can make restricted al U.S. Pat. No. 4,490,728 ejected fromthe chip an effective heat ♦ IJ02, IJ11, IJ12, surface, normal to thesink IJ20, IJ22 plane of the chip. ♦ Mechanical strength Through Inkflow is through the ♦ High ink flow ♦ Requires bulk ♦ Silverbrook, EPchip, chip, and ink drops are ♦ Suitable for silicon etching 0771 658 A2and forward ejected from the front pagewidth print related patent (‘upsurface of the chip. heads applications shooter’) ♦ High nozzle ♦ IJ04,IJ17, IJ18, packing density IJ24, IJ27-IJ45 therefore low manufacturingcost Through Ink flow is through the ♦ High ink flow ♦ Requires wafer ♦IJ01, IJ03, IJ05, chip, chip, and ink drops are ♦ Suitable for thinningIJ06, IJ07, IJ08, reverse ejected from the rear pagewidth print ♦Requires special IJ09, IJ10, IJ11, (‘down surface of the chip. headshandling during IJ14, IJ15, IJ16, shooter’) ♦ High nozzle manufactureIJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore low manufacturingcost Through Ink flow is through the ♦ Suitable for ♦ Pagewidth print ♦Epson Stylus actuator actuator, which is not piezoelectric print headsrequire ♦ Tektronix hot fabricated as part of heads several thousandmelt piezoelectric the same substrate as connections to drive ink jetsthe drive transistors. circuits ♦ Cannot be manufactured in standardCMOS fabs ♦ Complex assembly required INK TYPE Aqueous, Water based inkwhich ♦ Environmentally ♦ Slow drying ♦ Most existing ink dye typicallycontains: friendly Corrosive jets water, dye, surfactant, ♦ No odor ♦Bleeds on paper ♦ All IJ series ink humectant, and May jets biocide.strike through ♦ Silverbrook, EP Modem ink dyes have Cockles paper 0771658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which ♦ Environmentally ♦ Slowdrying ♦ IJ02, IJ04, IJ21, pigment typically contains: friendlyCorrosive IJ26, IJ27, IJ30 water, pigment, ♦ No odor ♦ Pigment may ♦Silverbrook, EP surfactant, humectant, ♦ Reduced bleed clog nozzles 0771658 A2 and and biocide. ♦ Reduced wicking ♦ Pigment may related patentPigments have an ♦ Reduced clog actuator applications advantage inreduced strike through mechanisms ♦ Piezoelectric ink- bleed, wickingand ♦ Cockles paper jets strike through. ♦ Thermal ink jets (withsignificant restrictions) Methyl MEK is a highly ♦ Very fast drying. ♦Odorous ♦ All IJ series ink Ethyl volatile solvent used ♦ Prints onvarious ♦ Flammable jets Ketone for industrial printing substrates suchas (MEK) on difficult surfaces metals and plastics such as aluminumcans. Alcohol Alcohol based inks ♦ Fast drying ♦ Slight odor ♦ All lJseries ink (ethanol 2- can be used where the ♦ Operates at sub- ♦Flammable jets butanol, printer must operate at freezing and others)temperatures below temperatures the freezing point of ♦ Reduced paperwater. An example of cockle this is in-camera ♦ Low cost consumerphotographic printing. Phase The ink is solid at ♦ No drying time- ♦High viscosity ♦ Tektronix hot change room temperature, and inkinstantly freezes ♦ Printed ink melt piezoelectric (hot melt) is meltedin the print on the print medium typically has a ink jets head beforejetting. ♦ Almost any print ‘waxy’ feel ♦ 1989 Nowak Hot melt inks aremedium can be used ♦ Printed pages U.S. Pat. No. 4,820,346 usually waxbased, ♦ No paper cockle may ‘block’ ♦ All IJ series ink with a meltingpoint occurs ♦ Ink temperature jets around 80° C. After ♦ No wicking maybe above the jetting the ink freezes occurs curie point of almostinstantly upon ♦ No bleed occurs permanent magnets contacting the print♦ No strike through ♦ Ink heaters medium or a transfer occurs consumepower roller. ♦ Long warm-up time Oil Oil based inks are ♦ Highsolubility ♦ High viscosity: ♦ All IJ series ink extensively used inmedium for some this is a significant jets offset printing. They dyeslimitation for use in have advantages in ♦ Does not cockle ink jets,which improved paper usually require a characteristics on ♦ Does notwick low viscosity. Some paper (especially no through paper short chainand wicking or cockle). multi-branched oils Oil soluble dies and have asufficiently pigments are required. low viscosity. ♦ Slow drying Micro-A microemulsion is a ♦ Stops ink bleed ♦ Viscosity higher ♦ All IJseries ink emulsion stable, self forming ♦ High dye than water jetsemulsion of oil, water, solubility ♦ Cost is slightly and surfactant.The ♦ Water, oil, and higher than water characteristic drop sizeamphiphilic soluble based ink is less than 100 nm, dies can be used ♦High surfactant and is determined by ♦ Can stabilize concentration thepreferred curvature pigment required (around of the surfactant.suspensions 5%)

What is claimed is:
 1. A method of manufacturing an ink jet printhead,the method comprising the steps of: (a) providing a silicon wafer havinga circuitry wafer layer including an electrical circuitry layer for theoperation of a thermal actuator on demand; (b) depositing a firstsacrificial layer on top of the circuitry wafer layer and etching thefirst sacrificial layer to define cavities for subsequent layers; (c)depositing a Young's modulus layer to form a first layer of the thermalactuator and a paddle member that extends from the thermal actuator; (d)depositing a conductive heater material layer on the Young's moduluslayer of the thermal actuator, the conductive heater material layerhaving a portion interconnected to the circuitry wafer layer; (e)depositing a second sacrificial layer and etching the second sacrificiallayer in preparation for the construction of nozzle chamber walls; (f)depositing a nozzle wall material layer over the second sacrificialmaterial layer to form the nozzle chamber walls and etching the nozzlewall material layer to define a port for the ejection of ink; and (g)etching away the sacrificial layers to release the paddle member and thethermal actuator, with the paddle member positioned in a nozzle chamberdefined by the formed nozzle chamber walls.
 2. A method as claimed inclaim 1 further comprising the step of etching an ink supply channelthrough the wafer for the supply of ink to the nozzle chamber.
 3. Amethod as claimed in claim 1 which includes depositing substantiallytitanium diboride to form the second material heater layer.
 4. A methodas claimed in claim 1 which includes depositing substantially glass toform the Young's modulus layer.
 5. A method as claimed in claim 1 whichincludes depositing substantially aluminium to form the firstsacrificial material layer.
 6. A method as claimed in claim 1 whichincludes constructing the nozzle chamber walls substantially from glass.7. A method as claimed in claim 1 wherein the first layer of the thermalactuator is positioned outside of the nozzle chamber walls while thepaddle is positioned within the actuator walls.
 8. A method as claimedin claim 7 wherein the nozzle chamber walls are formed to define a wallthrough which the first layer of the thermal actuator and the paddleextend so that said wall defines a fulcrum for movement of the paddletowards and away from the nozzle port, in use.
 9. A method as claimed inclaim 1 wherein a series of etchant holes are formed in the nozzle wallmaterial layer to facilitate etching of the sacrificial layers.
 10. Amethod as claimed in claim 1 wherein the wafer comprises a double-sidedpolished CMOS wafer.
 11. A method as claimed in claim 1 wherein thewafer is separated into separate printheads.